This invention relates to apparatus, systems and methods for converting energy present in ocean surface waves into electric energy.
A known system for capturing ocean surface wave energy includes: (a) a first structure (which may be or interchangeably referred to herein as a “shell” or “vessel” or “float”) which, when placed in a body of water, is designed to move up and down, generally, in phase with the waves in the water and thus absorb and/or release energy; (b) a second structure (which may be or interchangeably referred to herein as a “shaft”, “spar”, “column” or piston) which is either stationary or moves generally out of phase relative to the waves and the first structure; and (c) a mechanical or hydraulic power take-off (PTO) device coupled between the first and second structures and which in response to the relative motion between the first and second structures is designed to produce mechanical or hydraulic motion which is then converted into electrical energy.
Prior art power take-off (PTO) devices include combinations of hydraulic devices, pneumatic devices, and/or mechanical translators (e.g. rack and pinion gear system), and rotary electric generators of various types and forms (permanent magnet generator, induction generator). These devices convert the relative motion between the shell and shaft into mechanical or hydraulic motion which is then converted into electrical energy. These devices and the systems employing them tend to be inefficient, expensive to make and difficult to design for survivability.
To avoid some of these problems it has been suggested to use a linear electric generator (LEG) for a power take-off (PTO) device. However, known wave energy conversion systems utilizing linear electric generators have performance, cost, reliability and/or survivability limitations resulting from the configuration and/or the suggested type of linear electric generator. Deficiencies of existing wave energy conversion systems utilizing known linear electric generators include the following:    1. known linear electric generators have limited stroke or range of motion, limiting the amount of power that can be extracted, resulting in complex, expensive mechanical designs to limit the range of force applied to the power take-off device, and/or decreasing the survivability of the wave energy converter systems; and/or    2. in known linear electric generator systems, induction coils are an integral part of the shell or column (e.g. induction coils encircle one of the wave energy converter structural elements), resulting in complex and expensive mechanical designs; and/or    3. known linear electric generator magnet and induction coil assemblies must be housed together in a watertight enclosure, necessitating unreliable and/or expensive sealing devices at an air/water interface.These deficiencies are overcome in systems embodying the invention.